Many functions of an advanced electronic device, such as a mobile phone, are implemented in a system-on-a-chip (SoC) integrated circuit. The SoC consumes current that changes with the number and kind of operations it performs. Descriptions of an element in terms of current or power are interchangeable after scaling by a respective voltage. The operations performed can change rapidly, for example, a few nanoseconds. The change in current consumption can be large, for example, a few amps. This results in a large current time derivative (dI/dt) that can interfere with operation of the SoC.
A power distribution network supplies power, for example, as a voltage supply, to the SoC. The SoC may be packaged in an integrated-circuit package that may be mounted on an interconnection substrate, such as a printed circuit board, for connection with other components including, for example, a power supply and battery. The power distribution network includes connections through the printed circuit board and integrated-circuit package. The connections of the power distribution network can have substantial parasitic inductance. This inductance combined with the large current time derivatives can cause large spike-like dips in the supply voltage, also referred to as droop, in the voltage supplied to the SoC. The droop can be so large as to interfere with proper operation of the device.
The voltage level supplied to the SoC is generally increased (which may be referred to as guardbanding) by the amount of voltage droop so the “drooped” voltage is sufficient for proper operation of the SoC. Guardbanding the voltage level increases power consumption and is undesirable, for example, due to increased temperature and decreased battery duration. Some prior systems have attempted to reduce the voltage droop, for example, by reducing inductance in the power distribution network or adding decoupling capacitors on or close to the SoC. For example, external landside capacitors (LSCs) and embedded-passive-substrate (EPS) capacitors may be added during routing of the PDN. Added decoupling capacitors may only slightly reduce the voltage droop. Additionally, they can be size and cost prohibitive.